7L 



INTRODUCTION TO THE 



Cliffs and Rocks at Ardrossan, 

 Yorke's Peninsula. 



By Otto Tepper, Corresponding Member. 



The geological formations at Ardrossan, situated on the 

 eastern coast of Yorke's Peninsula, present some interesting 

 points, there being preserved here, not only deposits of the 

 oldest Tertiary formations hitherto known in the southern 

 parts of South Australia, but others showing more or less 

 metamorphic action and fossil remains, adjacent to rocks of 

 a highly crystalline character resting upon granite or 

 intruded by it. Though all the rocks mentioned in this 

 paper may be studied at some point or other within a mile 

 or two of the coast, yet the difficulties in the way of exact 

 determination are considerable, there being few places where 

 underlying strata are exposed, hill and dale inland being mostly 

 covered with dense' mallee scrub, or, where this is absent, the 

 almost universal surface limestone (travertine) and clay veil 

 the older deposits. Thus a good deal has to be inferred from 

 what can be observed at distant localities. 



The accompanying plans, diagrams, &c, illustrate the result* 

 of my observations. Fig. 1 is apian showing the topograjmieal 

 details of most deposits, as observed at the surface. Pig. 2 

 represents the relation of the strata in the direction of the line 

 forming the northern boundary of Section 77. Fig. 3 represents 

 the intercalation of some limestones and a silicious rock not 

 observed elsewhere and to be described in due course. Pigs. 

 4 and 5 illustrate details of the uppermost portion of the 

 f ossilif erous Tertiary rocks ; fig. 4 showing the first appearance of 

 the "Turritella grits" under the "Ardrossan clays and gravels;" 

 and fig. 5 the several constituent layers of the same, being 

 chiefly interesting on account of the fact that the " Ardrossan 

 clays," while at Ardrossan forming the foot of the sea cliffs, 

 the " grits " appear at the summit — here suddenly assume the 

 place of the upper portion of the " grits," ending abruptly, 

 but not divided by any distinct line of demarcation, which has 

 induced me to consider these characteristic red and white clays 

 as the lowermost member of the newer Tertiary strata, produced 

 by the disintegration of the older Tertiary rocks. 



